Abstract: Two zones, exhibiting glucose-6-phosphate dehydrogenase (G6PD) activity, were identified in lysates of thrombocytes from healthy persons by means of polyacrylamide gel disc electrophoresis; amount of the zones was increased up to 7 during the preinfarction period and up to II within the acute period myocardial infarction, three zones were found at the postinfarction period. Temperature optimum of the enzyme activity from thrombocytes was near 50 degrees in both the healthy persons and in the patients with acute myocardial infarction. After preincubation of G6PD within 10 min at 40 degrees and 60 degrees the enzymatic activity was similarly decreased by (50-55% and 85-90%, respectively, in thrombocyte preparations from healthy persons and from the patients with myocardial infarction.